Corneal collagen cross-linking in patients with keratoconus from the Dresden protocol to customized solutions:theoretical basis

Keratoconus is an ectatic condition characterized by gradual corneal thinning,corneal protrusion,progressive irregular astigmatism,corneal fibrosis,and visual impairment.The therapeutic options regarding improvement of visual function include glasses or soft contact lenses correction for initial stages,gas-permeable rigid contact lenses,scleral lenses,implantation of intrastromal corneal ring or corneal transplants for most advanced stages.In keratoconus cases showing disease progression corneal collagen crosslinking(CXL)has been proven to be an effective,minimally invasive and safe procedure.CXL consists of a photochemical reaction of corneal collagen by riboflavin stimulation with ultraviolet A radiation,resulting in stromal crosslinks formation.The aim of this review is to carry out an examination of CXL methods based on theoretical basis and mathematical models,from the original Dresden protocol to the most recent developments in the technique,reporting the changes proposed in the last 15y and examining the advantages and disadvantages of the various treatment protocols.Finally,the limits of non-standardized methods and the perspectives offered by a customization of the treatment are highlighted.

Detecting early changes in choroidal vascularity and thickness using optical coherence tomography in patients with corneal crosslinking for keratoconus

AIM:To investigate changes in choroidal thickness and vascularity in keratoconus patients treated with corneal crosslinking.METHODS:This study evaluated 28 eyes of 22 patients with keratoconus who underwent corneal crosslinking.The choroidal thicknesses were evaluated on enhanced depth imaging optical coherence tomography at the preoperative and postoperative 3d,1,and 3mo.Choroidal thickness in the four cardinal quadrants and the fovea were evaluated.The choroidal vascularity index was also calculated.RESULTS:There was no significant difference in central choroidal thickness between the preoperative and postoperative 3d,1mo(P>0.05).There was a significant increase in the 3mo(P=0.034)and a significant decrease in the horizontal choroidal vascularity index on the postoperative 3d(P=0.014),there was no statistically significant change in vertical axes and other visits in horizontal sections(P>0.05).CONCLUSION:This study sheds light on choroidal changes in postoperative corneal crosslinking for keratoconus.While it suggests the procedure’s relative safety for submacular choroid,more extensive research is necessary to confirm these findings and their clinical significance.

Efficacy of custom-made soft keratoconus lenses on corneal aberrations and photic phenomena in patients with keratoconus:a corneal topography imaging based study

AIM:To evaluate the efficacy of custom-made soft keratoconus(KC)lenses on corneal aberrations and photic phenomena in two different optical zones in patients with KC.METHODS:Sixty eyes of 42 patients with KC were examined at baseline and after fitting HydroCone(Toris K)soft silicone hydrogel lenses.Best spectacle-corrected visual acuity(BSCVA)and contact lens-corrected visual acuity(CLCVA)were recorded.Lower-and higher-order corneal aberrations(LOAs and HOAs)were measured with and without Toris K lenses and compared in central 4.5 mm and 7 mm zones.Mesopic pupil diameter and subjective photic phenomena were also assessed.RESULTS:Mean CLCVA was significantly improved compared to BSCVA(P<0.0001).Corneal curvature and refractive measurements were found to be significantly reduced by the use of Toris K lenses,except for posterior corneal curvature values.In the 4.5 mm central optical zone,all wavefront aberrations decreased significantly after lens fitting(P<0.0001).In contrast,in the 7 mm(peripheral)optical zone,values for HOAs,spherical and residual aberrations,and optical path differences were increased,while LOAs,trefoil,and quadrifoil coefficients were decreased.The rate of photic phenomena was significantly higher in participants with a pupil size>6.00 mm(85.7%).CONCLUSION:Toris K lenses provide good visual results and a significant reduction in central corneal aberrations in patients with KC but could cause an increase in peripheral aberrations.This practical and nonsurgical approach appears to be an effective method for the visual management of KC.

Assessment of the effects of intrastromal injection of adipose-derived stem cells in keratoconus patients

·AIM: To evaluate the efficacy and safety of intrastromal transplantation of adipose-derived stem cells(ASCs) in keratoconus patients.·METHODS: This study was conducted on 8 eyes of 8 patients with moderate to severe keratoconus. In the patients, ophthalmic assessments including visual acuity, refraction, slit lamp examination, fundoscopy, corneal topography, and confocal microscopy were performed. Autologous stem cells were used. The isolated stem cells were injected into the corneal stroma by using femtosecond laser. Surgical procedure was similar to intracorneal ring implantation. All patients were re-assessed 1, 3, and 6mo after surgery.·RESULTS: The baseline mean visual acuity was 0.48±0.18 and improved to 0.66±0.17 after surger y and final acuity increased by 1.85±0.80 lines(P=0.001).The mean spherical refraction of patients improved 0.34 ± 0.35 D(P=0.039), and the mean cylindrical refraction of patients improved 0.84±0.23 D(P=0.016). The mean flat keratometry decreased 0.78±0.71 D(P=0.017), and the mean steep keratometry decreased 0.59±0.68 D(P=0.023). The mean central corneal thickness of patients improved of 6.29±4.47 μm(P=0.03). The mean keratocyte density at the anterior and middle stroma of cornea increased(P<0.05) but remained stable at the posterior stroma after 6mo. All patients had no complications and their corneas remained transparent. ·CONCLUSION: Intrastromal transplantation of ASCs has positive effects on vision and refractive parameters in most patients with keratoconus. After six months, visual acuity improved moderately, corneal parameters reduced slightly, and stromal keratocytes density increased. This modality is safe, and patients do not have any complications.

Evaluation of corneal topographic,tomographic and biomechanical indices for detecting clinical and subclinical keratoconus:a comprehensive three-device study

AIM:To evaluate the diagnostic ability of topographic and tomographic indices with Pentacam and Sirius as well as biomechanical parameters with Corvis ST for the detection of clinical and subclinical forms of keratoconus(KCN).METHODS:In this prospective diagnostic test study,70 patients with clinical KCN,79 patients with abnormal findings in topography and tomography maps with no evidence on clinical examination(subclinical KCN),and 68 normal control subjects were enrolled.The accuracy of topographic,tomographic,and biomechanical parameters was evaluated using the area under the receiver operating characteristic curve(AUC)and cross-validation analysis.The Delong method was used for comparing AUCs.RESULTS:In distinguishing KCN from normal,all parameters showed statistically significant differences between the two groups(P<0.001).Indices with the perfect diagnostic ability(AUC≥0.999)were Sirius KCN vertex of back(KVb),Pentacam random forest index(PRFI),Pentacam index of height decentration(IHD),and Corvis integrated tomographic/biomechanical index(TBI).In distinguishing subclinical KCN from normal,Sirius symmetry index of back(SIb;AUC=0.908),Pentacam inferior-superior difference(IS)value(AUC=0.862),PRFI(AUC=0.847),and Corvis TBI(AUC=0.820)performed best.There were no significant differences between the highest AUCs within keratoconic groups(De Long,P>0.05).CONCLUSION:In clinical KCN,all topographic,tomographic,and biomechanical indices have acceptable outcomes in terms of sensitivity and specificity.However,in differentiating subclinical forms of KCN from normal corneas,curvature-based parameters(SIb and IS value)followed by integrated indices(PRFI and TBI)are the most powerful tools for early detection of KCN.

Trans-epithelial accelerated corneal cross-linking for keratoconus in children

The aim of the study is to evaluate the safety and effi cacy of trans-epithelial accelerated corneal cross-linking（TE-ACXL） in children with progressive keratoconus.Retrospective,case-series of 23 eyes of 14 children who underwent TE-ACXL.Evaluations were performed at baseline and 1,3,6,12 and 18 mo postoperatively.Mean follow-up time of 23.82±3.15 mo and mean age was 13.7±1.4 y（range 11 to 16 y）.Mean preoperative uncorrected distance visual acuity changed from 0.92±0.45 log MAR（20/160） to 0.71±0.40 log MAR（20/100）（P=0.001）.Mean keratometry（Km） changed from 53.87± 6.03 to 53.00±5.81（P=0.001）.Pachymetry did not have significant changes at last follow-up（P=0.30）.The mean preoperative sphere was-5.58±2.48 and-4.89±4.66 D（P=0.11） at last follow-up;refractive cylinder from-5.58±2.48 to-5.02±2.23（P=0.046）.In conclusion,tomographic and refractive stability are shown in over 91% of eyes with pediatric progressive keratoconus who underwent TE-ACXL.

Topographic characteristics of keratoconus among a sample of Jordanian patients

· AIM: To identify topographic characteristics of keratoconus in a Jordanian sample.· METHODS: This study characterized 210 corneas affected with keratoconus presenting to Jordan University Hospital. Patients were diagnosed based on clinical examinations and Pentacam imaging. Eyes of males(n =101) were of a similar proportion to females(n =109). All of the 111 patients were affected bilaterally.Ages ranged between 13 and 44 y with a mean age of25.2y.· RESULTS: Results revealed significant differences between males and females at the level of the flat curvature power, basement membrane thickness and size of the anterior chamber. Eyes were arranged in three groups based on severity levels: mild, moderate and severe determined by the mean curvature power(Km).Results show that the flat(K1) and steep(K2) curvature powers, corneal asphericity coefficient(QV), thinnest point, pachy apex and basement membrane thickness are significantly different among the three groups, but not the corneal and anterior chamber volumes.Morphological analyses, based on sagittal maps, show no differences in keratometric values between eyes with different sagittal patterns except for the vertical location of the pachy apex relative to the pupil center and the thinnest point. Eyes with the island front elevation map are significantly more affected than eyes with the U shape and the ridge pattern.· CONCLUSION: All keratometric values measured except for corneal and anterior chamber volumes vary significantly with disease severity. The vertical pachy apex location correlates well with severity levels while the horizontal location seems to have no effect. Ourstudy also indicates that front elevation maps may be a better predictor of the severity of keratoconus than sagittal maps.

In-vivo corneal biomechanical analysis of unilateral keratoconus

AIMTo evaluate and compare corneal biomechanical findings measured by ocular response analyzer, topographic and pachymetric findings in patients with unilateral keratoconus patients and healthy controls.METHODSThis is an observational, case-control study. Patients with keratoconus in one eye and forme fruste keratoconus in the fellow eye were compared with sex and age matched with controls healthy subjects. All subjects were evaluated with rotating scheimpflug imaging system. The receiver-operating-characteristic curves were analyzed to evaluate the sensitivity and specificity of the parameters.RESULTSTwenty-seven patients with keratoconus in one eye and forme fruste keratoconus in the fellow eye were compared with 40 eyes of 40 normal subjects. Corneal hysteresis (CH) was 8.0&#x000b1;1.7 mm Hg in keratoconus group, 8.3&#x000b1;1.6 mm Hg in forme fruste keratoconus group, and 9.8&#x000b1;1.6 mm Hg in control groups (P=0.54 between keratoconus and forme fruste keratoconus groups, P&#x0003c;0.01 between control group and other groups). Corneal resistance factor (CRF) was 7.1&#x000b1;2.2 mm Hg in keratoconus group, 7.8&#x000b1;1.2 mm Hg in forme fruste keratoconus group and 9.9&#x000b1;1.5 mm Hg in control group (P&#x0003c;0.001 between control group and other groups). Using receiver-operating-characteristic analysis, the area under curve values of the parameters to distinguish forme fruste keratoconus from control subjects were: CH (0.768), CRF (0.866). Best cut-off points were 9.3 mm Hg and 8.8 mm Hg for CH and CRF respectively.CONCLUSIONOcular response analyzer parameters (CH and CRF) are found to be significantly lower in forme fruste keratoconus patients compared to normal control subjects.

The correlation between keratoconus and eye rubbing: a review

Keratoconus is a non-inflammatory disorder which is gradual in development;corneal thinning and ectatic protrusion characterizes it. Keratoconus prevalence varies between different regions depending on several factors that affecting its prevalence. There are risk factors for developing keratoconus such as demographic and environmental factors. It was suggested that eye rubbing was associated with the development of keratoconus. The main aim of this review was to summarize the literature data about keratoconus and to identify the role of eyerubbing in the aetiology of the disease. A number of 24 articles was reviewed through the Pub Med, Google Scholar and Research Gates. There are many keywords used such as keratoconus, aetiology of keratoconus, eye rubbing, keratoconus prevalence, keratoconus and eye rubbing correlation. We concluded that eye rubbing causes the thinning of keratocyte, and the degree of effect of eye rubbing depends on the period and force of performing eye rubbing. It is recommended to avoid eye rubbing to prevent keratoconus, this can be achieved by avoiding itching and treating dryness of the eye and avoiding wearing eye lenses.

Corneal collagen crosslinking in keratoconus and other eye disease

Keratoconus is a condition characterized by biomechanical instability of the cornea, presenting in a progressive, asymmetric and bilateral way. Corneal collagen crosslinking(CXL) with riboflavin and Ultraviolet-A(UVA) is a new technique of corneal tissue strengthening that combines the use of riboflavin as a photo sensitizer and UVA irradiation. Studies showed that CXL was effective in halting the progression of keratoconus over a period of up to four years. The published studies also revealed a reduction of max K readings by more than 2 D, while the postoperative spherical equivalent(SEQ) was reduced by an average of more than 1 D and refractive cylinder decreased by about1 D. The major indication for the use of CXL is to inhibit the progression of corneal ecstasies, such as keratoconus and pellucid marginal degeneration. CXL may also be effective in the treatment and prophylaxis of iatrogenic keratectasia, resulting from excessively aggressive photo ablation. This treatment has been used to treat infectious corneal ulcers with apparent favorable results. Most recent studies demonstrate the beneficial impact of CXL for iatrogenic ecstasies, pellucid marginal degeneration, infectious keratitis, bullous keratopathy and ulcerative keratitis. Several long-term and short-term complications of CXL have been studied and documented. The possibility of a secondary infection after the procedure exists because the patient is subject to epithelial debridement and the application of a soft contact lens. Formation of temporary corneal haze,permanent scars, endothelial damage, treatment failure,sterile infiltrates, bullous keratopathy and herpes reactivation are the other reported complications of this procedure.

In vivo corneal confocal microscopic analysis in patients with keratoconus

AIM: To quantify corneal ultrastructure using laser scanning in vivo confocal microscopy(IVCM) in patients with keratoconus and control subjects. METHODS: Unscarred corneas of 78 keratoconic subjects without a history of contact lens use and 36age-matched control subjects were evaluated with slit-lamp examination(SLE), corneal topography and laser scanning IVCM. One eye was randomly chosen for analysis. Anterior and posterior stromal keratocyte,endothelial cell and basal epithelial cell densities and sub-basal nerve structure were evaluated.RESULTS: IVCM qualitatively demonstrated enlarged basal epithelial cells, structural changes in sub-basal and stromal nerve fibers, abnormal stromal keratocytes and keratocyte nuclei, and pleomorphism and enlargement of endothelial cells. Compared with control subjects, significant reductions in basal epithelial cell density( 5817 ± 306 cells / mm2 vs 4802 ±508 cells/mm2,P 【 0. 001), anterior stromal keratocyte density(800 ±111 cells/mm2 vs 555 ±115 cells/mm2, P 【0.001),posterior stromal keratocyte density(333±34 cells/mm2vs270 ±47 cells/mm2, P 【0.001), endothelial cell density(2875 ±223 cells/mm2 vs 2686 ±265 cells/mm2, P 【0.001),sub-basal nerve fiber density(31.2 ±8.4 nerves/mm2vs18.1 ±9.2 nerves/mm2, P 【0.001), sub-basal nerve fiber length(21.4±3.4 mm/mm2 vs 16.1±5.1 mm/mm2, P 【0.001),and sub-basal nerve branch density(median 50.0(first quartile 31.2- third quartile 68.7) nerve branches/mm2 vs median 25.0(first quartile 6.2- third quartile 45.3) nerve branches/mm2, P 【0.001) were observed in patients with keratoconus.CONCLUSION: Significant microstructural abnormalities were identified in all corneal layers in the eyes of subjects with keratoconus using IVCM. This non-invasive in vivo technique provides an important means to define and follow progress of microstructural changes in patients with keratoconus.

Femtosecond laser-assisted deep anterior lamellar keratoplasty for keratoconus and keratectasia

·AIM: To describe the initial outcomes and safety of femtosecond laser-assisted deep anterior lamellar keratoplasty(DALK) for keratoconus and post-LASIK keratectasia.·METHODS: In this non-comparative case series, 10 eyes of 9 patients underwent DALK procedures with a femtosecond laser(Carl Zeiss Meditec AG, Jena,Germany). Of the 9 patients, 7 had keratoconus and 2had post-LASIK keratectasia. A 500 kHz VisuMax femtosecond laser was used to perform corneal cuts on both donor and recipient corneas. The outcome measures were the uncorrected visual acuity(UCVA),best-corrected visual acuity(BCVA), corneal thickness,astigmatism, endothelial density count(EDC), and corneal power.·RESULTS: All eyes were successfully treated. Early postoperative evaluation showed a clear graft in all cases. Intraoperative complications included one case of a small Descemet’s membrane perforation.Postoperatively, there was one case of stromal rejection,one of loosened sutures, and one of wound dehiscence.A normal corneal pattern topography and transparency were restored, UCVA and BCVA improved significantly,and astigmatism improved slightly. There was no statistically significant decrease in EDC.· CONCLUSION: Our early results indicate that femtosecond laser-assisted deep anterior lamellar keratoplasty could improve UCVA and BCVA in patients with anterior corneal pathology. This approach shows promise as a safe and effective surgical choice in the treatment of keratoconus and post-LASIK keratectasia.

Contact lens impact on quality of life in keratoconus patients: rigid gas permeable versus soft siliconehydrogel keratoconus lenses

AIMTo determine the impact of rigid gas permeable (RGP) and silicone-hydrogel keratoconus lenses on the quality of life (QoL) in keratoconus (KCN) patients using the self-reported results from the Contact Lens Impact on Quality of Life (CLIQ) Questionnaire.METHODSFrom January 2013 to April 2013, 27 consecutive KCN patients who wore RGP contact lenses (conflexair100 UV KE Zeiss-W&#x000f6;hlk) or soft silicone-hydrogel contact lenses (SHCLs) for KCN (KeraSoft IC- Bausch&#x00026;Lomb or Hydrocone Toris K-Swiss lens) completed the CLIQ questionnaire.RESULTSThe mean age of 27 patients was 29.6&#x000b1;8.0y. Fifteen patients were RGP user. The groups were comparable with respect to the mean patient age, sex, and mean K values (P=0.1, P=0.8 and P=0.1, respectively). The mean CLIQperson measure was 42.8&#x000b1;5.5 in RGP group and 39.6&#x000b1;5.5 in SHCLs for KCN group (P=0.06). CLIQperson measure was positively correlated with steep K value (r=0.301, P=0.04). When eyes were stratified by visual acuity with contact lenses, the mean CLIQperson measure was 42.01&#x000b1;5.6 in eyes with a visual acuity of 20/20-20/25 (n=44) and 38.4&#x000b1;5.26 in eyes with a visual acuity of 20/32 or less (n=10; P=0.097).CONCLUSIONRGP lenses and SHCLs for KCN have similar impact on QoL.

Effects of contact lens wearing on keratoconus:a confocal microscopy observation

AIM： To evaluate the corneal cell morphology of new keratoconus patients wearing two different types of rigid gas-permeable（RGP） contact lenses for 1y.METHODS： Thirty nine eyes of 39 new keratoconus patients were selected and randomly fitted with two types of RGP contact lenses.Group 1 had 21 eyes with regular rigid gas-permeable（RRGP） contact lens and rest 18 eyes were in group 2 with specially designed rigid gas-permeable（SRGP） contact lens.Corneal cell morphology was evaluated using a slit scanning confocal microscope at no-lens wear and after 1y of contact lens wearing.RESULTS： After 1y of contact lens wearing in group 1,the mean anterior and posterior stromal keratocyte density were significantly less（P=0.006 and P=0.001,respectively） compared to no-lens wear.The mean cell area of anterior and posterior stromal keratocyte were also significantly different（P=0.005 and P=0.001） from no-lens wear.The anterior and posterior stromal haze increased by 18.74% and 23.81%,respectively after 1y of contact lens wearing.Whereas in group 2,statistically significant changes were observed only in cell density ＆ area of anterior stroma（P=0.001 and P=0.001,respectively） after 1y.While,level of anterior and posterior stromal haze increased by 16.67% and 11.11% after 1y of contact lens wearing.Polymegathism and pleomorphism also increased after 1y of contact lens wearing in both the contact lens groups.CONCLUSION： Confocal microscopy observation shows the significant alterations in corneal cell morphology of keratoconic corneas wearing contact lenses especially in group 1.The type of contact lens must be carefully selected to minimize changes in corneal cell morphology.

Expression of visual system homeobox 1 in human keratoconus

AIM: To investigate the expression of visual system homeobox 1(VSX1) and myofibroblast marker alpha smooth muscle actin(α-SMA) in keratoconus(KC). METHODS: Thirty corneal tissue were collected from KC patients after corneal transplantation and 15 normal donor corneas were obtained. All corneal tissues divided into 4 parts for different detections. Scanning electron microscopy was used to observe the ultrastructure of the specimens. VSX1 and α-SMA localization in cornea tissues was detected using immunofluorescence histochemistry. Reverse transcription-quantitative polymerase chain reaction(RT-qPCR) and Western blot were performed to analyze the expression level of VSX1 and α-SMA. RESULTS: Compared to normal cornea tissue, the collagen fibers in KC stroma were distortional and attenuated and keratocytes were abnormally changed. VSX1 and α-SMA located in the corneal stroma. The mRNA and protein expression level of VSX1 in KC were about 3 times as high as that of normal tissue(P<0.001). α-SMA was hardly expressed in the normal corneas, however, its expression in the KC was about 1.5 times higher than that of the normal corneas(P<0.0001). CONCLUSION: Compared with normal corneal the expression of VSX1 and α-SMA in KC both increased. VSX1 is related to the activation of keratocytes and involved in the pathogenesis of keratoconus.

Effects of vernal and allergic conjunctivitis on severity of keratoconus

AIM: To demonstrate the effects of two different types of allergic conjunctivitis on severity of keratoconus (KC). ·METHODS: We retrospectively reviewed the medical records of 171 KC patients referred between June 2010 and June 2011. The KC patients were divided into 3 groups as KC (group A), KC with vernal keratoconjunctivitis (VKC) (group B) and KC with allergic conjunctivitis (AC) (group C). Main outcome measures were demographic and ocular clinical features including age at presentation, gender, spherical equivalent (SE), best spectacle corrected visual acuity (BCVA), mean keratometric measurement (Km), central corneal thickness (CCT), and intraocular pressure (IOP). Groups were compared in term of study variables. · RESULTS: The median age at presentation was significantly lower in group B (P 【0.001). According to the median SE (P =0.003), BCVA(P =0.022), Km(P 【0.001), CCT (P =0.015) and Amsler-Krumeich classification (P 【 0.001), KC was more severe in group B. There was no significant difference in terms of IOP and corrected IOP among the groups (P =0.44), however there were 4 patients who had increased corrected IOP developed after topical corticosteroid use in group B. The differences among the groups persisted even after controlling for age and gender. · CONCLUSION: Our findings demonstrated a more severe KC in VKC patients despite their younger age which suggests evaluation of VKC patients as a separate group in keratoconus disease.

Long-term outcomes of penetrating keratoplasty in keratoconus: analysis of the factors associated with final visual acuities

AIM:To investigate the long-term results of penetrating keratoplasty(PK)in patients with keratoconus(KC)and to evaluate factors that might influence the final visual outcome.METHODS:We retrospectively reviewed the data of all patients with clinical KC who had undergone PK by a single corneal surgeon in a single center from May 1980to December 2005.The age of the patients,preoperative best-corrected visual acuity(BCVA),corneal thickness,death to preservation time,and preservation to transplantation time were recorded.Additionally,postoperative complications such as graft rejection,development of glaucoma and specular microscopy were checked during the follow-up.RESULTS:Sixty-nineeyesfrom69patientswerefinally included.The follow-up period was 8.64±6.13y.Graft rejection occurred in 4 eyes of 69 cases(5.8%),and the time to graft rejection was 2.1±1.3y.A Kaplan-Meier survival analysis showed that the estimated cumulative probability of graft rejection at 6,13,and 17y after PK were 95.6%,90.0%,and 78.8%,respectively.When we evaluated factors that might influence final BCVA in eyes,no disparity donor-host trephine size(same graft size)as well as higher spherical equivalent,and average Kvalue were associated with higher final BCVA.(P=0.006,0.051,0.092,and 0.021 in eyes with follow-up【8y;P=0.068,0.065,and 0.030 in eyes with follow-up≥8y,respectively).CONCLUSION:The long-term results of PK in patients with KC were favorable with a high percentage of good BCVA.Less myopic change and low average K-reading,as well as a surgical technique using the same size donor-recipient button may provide better visual outcomes particularly in patients with KC.

Comparison of contrast sensitivity and visual acuity between deep anterior lamellar keratoplasty and penetrating keratoplasty in patients with keratoconus

AIM: To evaluate postoperative visual acuity and contrast sensitivity results following deep anterior lamellar keratoplasty (DALK) and penetrating keratoplasty (PK) in patients with keratoconus (KC). METHODS: All the patients’ records with KC who had PK or DALK surgery between May 2010 and May 2011 were retrospectively reviewed. Sixty patients who underwent successful corneal transplantation for KC: 30 eyes underwent DALK and 30 eyes underwent PK were included in this study. Preoperative and postoperative mean logarithm of the minimum angle of resolution (logMAR) uncorrected visual acuity (UCVA), logMAR best spectacle-corrected visual acuity (BSCVA) and intraocular pressure (IOP) were evaluated. Contrast sensitivity tests (CS) were done preoperative and 2 months after all sutures had removed. All surgeries were performed under regional anesthesia (retrobulbar anesthesia) by 1 surgeon (B.K.) who was experienced in penetrating and lamellar keratoplasty techniques. RESULTS: The mean age of the DALK group was 29.67±4.95 (range 18-40) years and the PK group was 28.7±3.53 (range 18-39) years. Preoperatively there was no significant difference in the logMAR UCVA, logMAR BSCVA and IOP between the DALK (1.281±0.56; 0.97±0.85; 12.07±2.12mmHg) and PK (1.34±0.21; 0.98±0.21; 13±2.12mmHg) groups. One-year after surgery there was no significant difference in the mean logMAR UCVA and IOP between the DALK (0.46±0.37; 11.73±2.1mmHg) and PK (0.38±0.21; 12±2.12mmHg) groups. The mean contrast sensitivity was evaluated by CC-100 Topcon LCD at 1.5, 2.52, 4.23, 7.10 and 11.91 cycles per degree (cs/deg) spatial frequencies before and 2 months after the all sutures had removed. CONCLUSION: All patients with keratoconus in both DALK and PK groups performed good visual function postoperatively. The mean contrast sensitivity increased considerably at all spatial frequencies compared with preoperative levels in the DALK and PK groups. The mean post-operative evaluation of contrast sensitivity measurements was not significantly different between the two groups.

Corneal epithelial thickness analysis of forme fruste keratoconus with optical coherence tomography

AIM:To explore the significance of corneal epithelial thickness analysis in diagnosing early keratoconus.METHODS:There were 26 clinical keratoconus,21 forme fruste keratoconus,40 high corneal astigmatism(ΔK)and 40 low ΔK eyes involved in the study.Fourierdomain optical coherence tomography was used to measure the corneal epithelial thickness of four groups.The morphological features of topographic map and the thickness of corneal epithelial thinnest point were analyzed.The distribution curve of corneal epithelial thickness at 45°,90°,and 135° axial directions that are through the pupil center was also analyzed.One-way ANOVA was performed to compare the data.RESULTS:The topographic map of forme fruste keratoconus corneal epithelial thickness was uniformity shape;crater shape existed only in clinical keratoconus group;and central island shape mainly existed in highΔK group.The thinnest point of corneal epithelial thickness of forme fruste keratoconus group was significantly lower than that of low ΔK group(P=0.022).The thickness of corneal epithelium in the forme fruste keratoconus at 90°was thinner than that in the low astigmatism group at -1,and -2 mm points(P_(-1mm)=0.015,P_(-2mm)=0.036).CONCLUSION:The analysis of the thinnest point in forme fruste keratoconus corneal epithelium appears earlier than corneal epithelial remodeling.The topographic map of corneal epithelium in high ΔK eyes appears in central island shape,and can be used for the differential diagnosis of early keratoconus.

Combined corneal CXL and photorefractive keratectomy for treatment of keratoconus: a review

Keratoconus and iatrogenic keratectasia are the corneal ectatic disorders occurring due to biomechanical weakening of the cornea resulting in distorted images,myopia, and irregular astigmatism. Corneal collagen cross-linking(CXL) is performed to arrest keratoconus successfully. The main aim of this review is to discuss the safety and efficacy of the adjuvant therapies, such as the combination of CXL and photorefractive keratectomy(PRK) for the treatment of corneal ectatic disorders. A comprehensive literature search was performed using PubM ed, MEDLINE, and Scopus using keywords ‘collagen’‘keratoconus’,‘keratectasia’,‘collagen cross-linking’,and ‘photorefractive keratectomy’. Search results were restricted to clinical studies published in English. Corneal CXL effectively arrests the progression of keratoconus by enhancing corneal rigidity. However, functional vision is not improved by cross-linking. Combining CXL to refractive surgeries such as topography-guided PRK or transepithelial PRK is found to be a safe and effective method in providing corneal stability as well as significantly improving functional visual acuity with few minor complications. This combined technique also prevents regression of keratoconus and reduce the risk of keratectasia. CXL combined with PRK is a promising therapeutic approach in ophthalmology that can be successfully used to treat progressive keratoconus and other corneal ectatic disorders and to enhance visual acuity.